Lithographic apparatus and a device manufacturing method

ABSTRACT

An immersion lithographic apparatus is provided having a substrate table including a drain configured to receive immersion fluid which leaks into a gap between an edge of a substrate on the substrate table and an edge of a recess in which the substrate is located. A thermal conditioning system is provided to thermally condition at least the portion of the recess supporting the substrate by directing one or more jets of fluid onto a reverse side of the section supporting the substrate.

This application is a continuation of U.S. patent application Ser. No.13/010,002, filed Jan. 20, 2011, now allowed, which claims priority andbenefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent ApplicationNo. 61/297,414, entitled “A Lithographic Apparatus and A DeviceManufacturing Method”, filed on Jan. 22, 2010. The content of eachapplication is incorporated herein in its entirety by reference.

FIELD

The present invention relates to a lithographic apparatus and a devicemanufacturing method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.comprising part of, one, or several dies) on a substrate (e.g. a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. In an embodiment, the liquid isdistilled water, although another liquid can be used. An embodiment ofthe invention will be described with reference to liquid. However,another fluid may be suitable, particularly a wetting fluid, anincompressible fluid and/or a fluid with higher refractive index thanair, desirably a higher refractive index than water. Fluids excludinggases are particularly desirable. The point of this is to enable imagingof smaller features since the exposure radiation will have a shorterwavelength in the liquid. (The effect of the liquid may also be regardedas increasing the effective numerical aperture (NA) of the system andalso increasing the depth of focus.) Other immersion liquids have beenproposed, including water with solid particles (e.g. quartz) suspendedtherein, or a liquid with a nano-particle suspension (e.g. particleswith a maximum dimension of up to 10 nm). The suspended particles may ormay not have a similar or the same refractive index as the liquid inwhich they are suspended. Other liquids which may be suitable include ahydrocarbon, such as an aromatic, a fluorohydrocarbon, and/or an aqueoussolution.

Submersing the substrate or substrate and substrate table in a bath ofliquid (see, for example, U.S. Pat. No. 4,509,852) means that there is alarge body of liquid that must be accelerated during a scanningexposure. This requires additional or more powerful motors andturbulence in the liquid may lead to undesirable and unpredictableeffects.

In an immersion apparatus, immersion fluid is handled by a fluidhandling system, device structure or apparatus. In an embodiment thefluid handling system may supply immersion fluid and therefore be afluid supply system. In an embodiment the fluid handling system may atleast partly confine immersion fluid and thereby be a fluid confinementsystem. In an embodiment the fluid handling system may provide a barrierto immersion fluid and thereby be a barrier member, such as a fluidconfinement structure. In an embodiment the fluid handling system maycreate or use a flow of gas, for example to help in controlling the flowand/or the position of the immersion fluid. The flow of gas may form aseal to confine the immersion fluid so the fluid handling structure maybe referred to as a seal member; such a seal member may be a fluidconfinement structure. In an embodiment, immersion liquid is used as theimmersion fluid. In that case the fluid handling system may be a liquidhandling system. In reference to the aforementioned description,reference in this paragraph to a feature defined with respect to fluidmay be understood to include a feature defined with respect to liquid.

SUMMARY

During the performance of a lithographic process, one or more sources ofheat may introduce temperature variations across one or more elementswithin the lithographic apparatus. There may also be temperaturevariations in time. Such temperature distributions may introduce errorswithin the lithographic process.

It is desirable, for example, to provide a lithography process in whichprocess errors introduced by one of more heat sources may be reduced orminimized.

According to an aspect, there is provided an immersion lithographicapparatus, comprising:

a substrate table including a recess having a support section configuredto support a substrate;

a drain in the substrate table, the drain configured to receive animmersion fluid which

leaks, in use, into a gap between an edge of a substrate on thesubstrate table and an edge of the recess; and

a thermal conditioning system configured to thermally condition thesupport section of the recess, the thermal conditioning systemcomprising an aperture configured to direct a jet of fluid onto areverse side of the support section of the recess that is opposite to asupport side that supports the substrate.

According to an aspect, there is provided a device manufacturing methodcomprising:

providing a substrate to a recess in a substrate table, the recesshaving a support section configured to support the substrate;

providing immersion fluid to an upper surface of the substrate;

extracting immersion fluid that leaks into a gap between an edge of thesubstrate and an edge of the recess through a drain in the substratetable; and

thermally conditioning the support section of the recess by directing ajet of fluid onto a reverse side of the support section of the recessthat is opposite a support side that supports the substrate.

According to an aspect, there is provided a lithographic apparatus,comprising:

a substrate table including a recess having a support section configuredto support a substrate, and a peripheral section surrounding the recess;and

a thermal conditioning system configured to thermally condition thesupport section of the recess and the peripheral section of thesubstrate table, the thermal conditioning system comprising an apertureconfigured to direct a jet of fluid onto a reverse side of the supportsection of the recess that is opposite to a support side that supportsthe substrate, and an aperture configured to direct a jet of fluid ontoa portion of the peripheral section of the substrate table.

According to an aspect, there is provided a device manufacturing methodcomprising:

providing a substrate to a recess in a substrate table, the recesshaving a support section configured to support the substrate and thesubstrate table having a peripheral section surrounding the recess;

thermally conditioning the support section of the recess by directing ajet of fluid onto a reverse side of the support section of the recessthat is opposite a support side that supports the substrate; and

thermally conditioning the peripheral section of the substrate table bydirecting a jet of fluid onto a portion of the peripheral section of thesubstrate table.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIGS. 2 and 3 depict a liquid supply system for use in a lithographicprojection apparatus;

FIG. 4 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 5 depicts a further liquid supply system for use in a lithographicprojection apparatus;

FIG. 6 depicts a portion of a substrate table according to an embodimentof the invention;

FIG. 7 depicts a portion of a substrate table according to an embodimentof the invention;

FIG. 8 depicts a portion of a substrate table according to an embodimentof the invention;

FIG. 9 depicts a portion of a substrate table according to an embodimentof the invention;

FIG. 10 depicts a portion of a substrate table according to anembodiment of the invention;

FIG. 11 depicts a portion of a substrate table according to anembodiment of the invention;

FIG. 12 depicts a portion of a substrate table according to anembodiment of the invention;

FIG. 13 depicts a portion of a substrate table according to anembodiment of the invention;

FIG. 14 depicts a portion of a thermal conditioning system according tothe invention;

FIG. 15 depicts a portion of a thermal conditioning system according tothe invention;

FIG. 16 depicts a portion of a thermal conditioning system according tothe invention;

FIG. 17 depicts a control system for a thermal conditioning systemaccording to an embodiment of the invention;

FIG. 18 depicts a portion of a thermal conditioning system according toan embodiment of the invention; and

FIG. 19 depicts a portion of a substrate table according to anembodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to oneembodiment of the invention. The apparatus comprises;

-   -   an illumination system (illuminator) IL configured to condition        a radiation beam B (e.g. UV radiation or DUV radiation);    -   a support structure (e.g. a mask table) MT constructed to        support a patterning device (e.g. a mask) MA and connected to a        first positioner PM configured to accurately position the        patterning device MA in accordance with certain parameters;    -   a substrate table (e.g. a wafer table) WT constructed to hold a        substrate (e.g. a resist-coated wafer) W and connected to a        second positioner PW configured to accurately position the        substrate W in accordance with certain parameters; and    -   a projection system (e.g. a refractive projection lens system)        PS configured to project a pattern imparted to the radiation        beam B by patterning device MA onto a target portion C (e.g.        comprising one or more dies) of the substrate W.

The illumination system IL may include various types of opticalcomponents, such as refractive, reflective, magnetic, electromagnetic,electrostatic or other types of optical components, or any combinationthereof, for directing, shaping, or controlling radiation.

The support structure MT holds the patterning device MA. It holds thepatterning device MA in a manner that depends on the orientation of thepatterning device MA, the design of the lithographic apparatus, andother conditions, such as for example whether or not the patterningdevice MA is held in a vacuum environment. The support structure MT canuse mechanical, vacuum, electrostatic or other clamping techniques tohold the patterning device MA. The support structure MT may be a frameor a table, for example, which may be fixed or movable as required. Thesupport structure MT may ensure that the patterning device MA is at adesired position, for example with respect to the projection system PS.Any use of the terms “reticle” or “mask” herein may be consideredsynonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device MA may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore tables at least one or all of which may hold a substrate (and/ortwo or more patterning device tables). In such “multiple stage” machinesthe additional tables may be used in parallel, or preparatory steps maybe carried out on one or more tables while one or more other tables arebeing used for exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source SO and the lithographic apparatus may beseparate entities, for example when the source SO is an excimer laser.In such cases, the source SO is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDcomprising, for example, suitable directing mirrors and/or a beamexpander. In other cases the source SO may be an integral part of thelithographic apparatus, for example when the source SO is a mercurylamp. The source SO and the illuminator IL, together with the beamdelivery system BD if required, may be referred to as a radiationsystem.

The illuminator IL may comprise an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator IL can be adjusted. In addition, the illuminator IL maycomprise various other components, such as an integrator IN and acondenser CO. The illuminator IL may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section. Similar to the source SO, the illuminator IL may or maynot be considered to form part of the lithographic apparatus. Forexample, the illuminator IL may be an integral part of the lithographicapparatus or may be a separate entity from the lithographic apparatus.In the latter case, the lithographic apparatus may be configured toallow the illuminator IL to be mounted thereon. Optionally, theilluminator IL is detachable and may be separately provided (forexample, by the lithographic apparatus manufacturer or anothersupplier).

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device MA. Having traversed the patterningdevice MA, the radiation beam B passes through the projection system PS,which focuses the beam onto a target portion C of the substrate W. Withthe aid of the second positioner PW and position sensor IF (e.g. aninterferometric device, linear encoder or capacitive sensor), thesubstrate table WT can be moved accurately, e.g. so as to positiondifferent target portions C in the path of the radiation beam B.Similarly, the first positioner PM and another position sensor (which isnot explicitly depicted in FIG. 1) can be used to accurately positionthe patterning device MA with respect to the path of the radiation beamB, e.g. after mechanical retrieval from a mask library, or during ascan. In general, movement of the support structure MT may be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which form part of the firstpositioner PM. Similarly, movement of the substrate table WT may berealized using a long-stroke module and a short-stroke module, whichform part of the second positioner PW. In the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort-stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2. Although the substratealignment marks as illustrated occupy dedicated target portions, theymay be located in spaces between target portions C (these are known asscribe-lane alignment marks). Similarly, in situations in which morethan one die is provided on the patterning device MA, the patterningdevice alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the followingmodes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to theradiation beam B is projected onto a target portion C at one time (i.e.a single static exposure). The substrate table WT is then shifted in theX and/or Y direction so that a different target portion C can beexposed. In step mode, the maximum size of the exposure field limits thesize of the target portion C imaged in a single static exposure.

2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the radiation beam Bis projected onto a target portion C (i.e. a single dynamic exposure).The velocity and direction of the substrate table WT relative to thesupport structure MT may be determined by the (de-)magnification andimage reversal characteristics of the projection system PS. In scanmode, the maximum size of the exposure field limits the width (in thenon-scanning direction) of the target portion C in a single dynamicexposure, whereas the length of the scanning motion determines theheight (in the scanning direction) of the target portion C.

3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the radiationbeam is projected onto a target portion C. In this mode, generally apulsed radiation source is employed and the programmable patterningdevice is updated as required after each movement of the substrate tableWT or in between successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Arrangements for providing liquid between a final element of theprojection system and the substrate can be classed into at least twogeneral categories. These are the bath type arrangement and the socalled localized immersion system. In the bath type arrangementsubstantially the whole of the substrate and optionally part of thesubstrate table is submersed in a bath of liquid. The so calledlocalized immersion system uses a liquid supply system in which liquidis only provided to a localized area of the substrate. In the lattercategory, the space filled by liquid is smaller in plan than the topsurface of the substrate and the area filled with liquid remainssubstantially stationary relative to the projection system while thesubstrate moves underneath that area. A further arrangement, to which anembodiment of the invention is directed, is the all wet solution inwhich the liquid is unconfined. In this arrangement substantially thewhole top surface of the substrate and all or part of the substratetable is covered in immersion liquid. The depth of the liquid coveringat least the substrate is small. The liquid may be a film, such as athin film, of liquid on the substrate. Any of the liquid supply devicesof FIGS. 2-5 may be used in such a system; however, sealing features arenot present, are not activated, are not as efficient as normal or areotherwise ineffective to seal liquid to only the localized area. Fourdifferent types of localized liquid supply systems are illustrated inFIGS. 2-5.

One of the arrangements proposed is for a liquid supply system toprovide liquid on only a localized area of the substrate and in betweenthe final element of the projection system and the substrate using aliquid confinement system (the substrate generally has a larger surfacearea than the final element of the projection system). One way which hasbeen proposed to arrange for this is disclosed in PCT patent applicationpublication no. WO 99/49504. As illustrated in FIGS. 2 and 3, liquid issupplied by at least one inlet onto the substrate, desirably along thedirection of movement of the substrate relative to the final element,and is removed by at least one outlet after having passed under theprojection system. That is, as the substrate is scanned beneath theelement in a −X direction, liquid is supplied at the +X side of theelement and taken up at the −X side. FIG. 2 shows the arrangementschematically in which liquid is supplied via inlet and is taken up onthe other side of the element by outlet which is connected to a lowpressure source. The arrows above the substrate W illustrate thedirection of liquid flow, and the arrow below the substrate Willustrates the direction of movement of the substrate table. In theillustration of FIG. 2 the liquid is supplied along the direction ofmovement of the substrate relative to the final element, though thisdoes not need to be the case. Various orientations and numbers of in-and out-lets positioned around the final element are possible, oneexample is illustrated in FIG. 3 in which four sets of an inlet with anoutlet on either side are provided in a regular pattern around the finalelement. Arrows in liquid supply and liquid recovery devices indicatethe direction of liquid flow.

A further immersion lithography solution with a localized liquid supplysystem is shown in FIG. 4. Liquid is supplied by two groove inlets oneither side of the projection system PS and is removed by a plurality ofdiscrete outlets arranged radially outwardly of the inlets. The inletsand outlets can be arranged in a plate with a hole in its center andthrough which the projection beam is projected. Liquid is supplied byone groove inlet on one side of the projection system PS and removed bya plurality of discrete outlets on the other side of the projectionsystem PS, causing a flow of a thin film of liquid between theprojection system PS and the substrate W. The choice of whichcombination of inlet and outlets to use can depend on the direction ofmovement of the substrate W (the other combination of inlet and outletsbeing inactive). In the cross-sectional view of FIG. 4, arrowsillustrate the direction of liquid flow in inlets and out of outlets.

In European patent application publication no. EP 1420300 and UnitedStates patent application publication no. US 2004-0136494, each herebyincorporated in their entirety by reference, the idea of a twin or dualstage immersion lithography apparatus is disclosed. Such an apparatus isprovided with two tables for supporting a substrate. Levelingmeasurements are carried out with a table at a first position, withoutimmersion liquid, and exposure is carried out with a table at a secondposition, where immersion liquid is present. In an arrangement, theapparatus has only one table, or has two tables of which only one cansupport a substrate.

PCT patent application publication WO 2005/064405 discloses an all wetarrangement in which the immersion liquid is unconfined. In such asystem the whole top surface of the substrate is covered in liquid. Thismay be advantageous because then the whole top surface of the substrateis exposed to the substantially same conditions. This has an advantagefor temperature control and processing of the substrate. In WO2005/064405, a liquid supply system provides liquid to the gap betweenthe final element of the projection system and the substrate. Thatliquid is allowed to leak (or flow) over the remainder of the substrate.A barrier at the edge of a substrate table prevents the liquid fromescaping so that it can be removed from the top surface of the substratetable in a controlled way. Although such a system improves temperaturecontrol and processing of the substrate, evaporation of the immersionliquid may still occur. One way of helping to alleviate that problem isdescribed in United States patent application publication no. US2006/0119809. A member is provided which covers the substrate in allpositions and which is arranged to have immersion liquid extendingbetween it and the top surface of the substrate and/or substrate tablewhich holds the substrate.

Another arrangement which has been proposed is to provide the liquidsupply system with a fluid handling structure. The fluid handlingstructure may extend along at least a part of a boundary of the spacebetween the final element of the projection system and the substratetable. Such an arrangement is illustrated in FIG. 5. The fluid handlingstructure is substantially stationary relative to the projection systemin the XY plane though there may be some relative movement in the Zdirection (in the direction of the optical axis). A seal is formedbetween the fluid handling structure and the surface of the substrate.In an embodiment, a seal is formed between the fluid handling structureand the surface of the substrate and may be a contactless seal such as agas seal. Such a system is disclosed in United States patent applicationpublication no. US 2004-0207824. In another embodiment the fluidhandling structure has a seal which is a non-gaseous seal, and so may bereferred to as a liquid confinement structure.

FIG. 5 schematically depicts a localized liquid supply system or fluidhandling structure or device with a body 12 forming a barrier member orliquid confinement structure, which extends along at least a part of aboundary of the space 11 between the final element of the projectionsystem PS and the substrate table WT or substrate W. (Please note thatreference in the following text to surface of the substrate W alsorefers in addition or in the alternative to a surface of the substratetable WT, unless expressly stated otherwise.) The liquid handlingstructure is substantially stationary relative to the projection systemPS in the XY plane though there may be some relative movement in the Zdirection (generally in the direction of the optical axis). In anembodiment, a seal is formed between the body 12 and the surface of thesubstrate W and may be a contactless seal such as a gas seal or fluidseal.

The fluid handling structure at least partly contains liquid in thespace 11 between a final element of the projection system PS and thesubstrate W. A contactless seal, such as a gas seal 16, to the substrateW may be formed around the image field of the projection system PS sothat liquid is confined within the space 11 between the substrate Wsurface and the final element of the projection system PS. The space 11is at least partly formed by the body 12 positioned below andsurrounding the final element of the projection system PS. Liquid isbrought into the space 11 below the projection system PS and within thebody 12 by liquid inlet 13. The liquid may be removed by liquid outlet13. The body 12 may extend a little above the final element of theprojection system PS. The liquid level rises above the final element sothat a buffer of liquid is provided. In an embodiment, the body 12 hasan inner periphery that at the upper end closely conforms to the shapeof the projection system PS or the final element thereof and may, e.g.,be round. At the bottom, the inner periphery closely conforms to theshape of the image field, e.g., rectangular, though this need not be thecase. The inner periphery may be any shape, for example the innerperiphery may conform to the shape of the final element of theprojection system. The inner periphery may be round.

The liquid is contained in the space 11 by the gas seal 16 which, duringuse, is formed between the bottom of the body 12 and the surface of thesubstrate W. The gas seal 16 is formed by gas, e.g. air or synthetic airbut, in an embodiment, N₂ or another inert gas. The gas in the gas seal16 is provided under pressure via inlet 15 to the gap between body 12and substrate W. The gas is extracted via outlet 14. The overpressure onthe gas inlet 15, vacuum level on the outlet 14 and geometry of the gapare arranged so that there is a high-velocity gas flow inwardly thatconfines the liquid. The force of the gas on the liquid between the body12 and the substrate W contains the liquid in a space 11. Theinlets/outlets may be annular grooves which surround the space 11. Theannular grooves may be continuous or discontinuous. The flow of gas iseffective to contain the liquid in the space 11. Such a system isdisclosed in United States patent application publication no. US2004-0207824.

The example of FIG. 5 is a so called localized area arrangement in whichliquid is only provided to a localized area of the top surface of thesubstrate W at any one time. Other arrangements are possible, includingfluid handling structures which make use of a single phase extractor ora two phase extractor as disclosed, for example, in United States patentapplication publication no US 2006-0038968. In an embodiment, a singleor two phase extractor may comprise an inlet which is covered in aporous material. In an embodiment of a single phase extractor the porousmaterial is used to separate liquid from gas to enable single-liquidphase liquid extraction. A chamber downstream of the porous material ismaintained at a slight under pressure and is filled with liquid. Theunder pressure in the chamber is such that the meniscuses formed in theholes of the porous material prevent ambient gas from being drawn intothe chamber. However, when the porous surface comes into contact withliquid there is no meniscus to restrict flow and the liquid can flowfreely into the chamber. The porous material has a large number of smallholes, e.g. of diameter in the range of 5 to 300 μm, desirably 5 to 50μm. In an embodiment, the porous material is at least slightly lyophilic(e.g., hydrophilic), i.e. having a contact angle of less than 90° to theimmersion liquid, e.g. water.

Many other types of liquid supply system are possible, for example a gasdrag arrangement where a liquid meniscus is pinned at outlet openings bytwo phase extraction such as is disclosed in United States patentapplication publication nos US 2009-0279060 and US 2009-0279062, eachhereby incorporated in its entirety by reference. The invention is notlimited to any particular type of liquid supply system. The inventionmay be advantageous for use with a confined immersion system in whichthe liquid between the final element of the projection system and thesubstrate is confined, for example, in optimizing the use. However, theinvention may be used with any other type of liquid supply system.

FIG. 6 schematically depicts a portion of a substrate table WT accordingto an embodiment of the invention. As shown, the substrate table WTincludes a central section 51 to support the substrate W and aperipheral section 52 that surrounds the central section 51. The centralsection 51 includes a support section 53 which may include protrusions54 to support the underside of the substrate W. The space surroundingthe protrusions 54 may be evacuated in order to secure the substrate Wto the support section 53.

The support section 53 of the central section 51 of the substrate tableWT may be arranged to form a recess within the substrate table WT. Therecess may also be partially defined by the peripheral section 52. Forexample, as depicted in FIG. 6, the substrate table WT may be configuredsuch that the upper surface of the peripheral section 52 issubstantially coplanar with the upper surface of a substrate W supportedby the substrate table WT. An edge of the peripheral section 52 maydefine the edge of the recess of the substrate table WT in which thesubstrate W is supported.

The peripheral section 52 may include a drain, which is configured toreceive immersion fluid which leaks, in use, into a gap 55 between theedge of the substrate W and the edge of the recess. Extraction throughthe drain may be used to remove bubbles from the gap between the edge ofthe substrate W and the edge of the recess in the substrate table WT.

As shown in FIG. 6, the drain may include an opening 61 through whichthe immersion liquid may pass to an extraction conduit 62. For example,the opening 61 may be provided in the form of a channel extending aroundthe peripheral section 52 of the substrate table WT. Alternatively oradditionally, the opening 61 may be provided in the form of a pluralityof discrete openings. As shown, the drain may include a cover section 63that extends across the opening 61 to the edge of the recess in whichthe substrate W is supported and be arranged such that the immersionliquid passes under the cover 63 before entering the opening 61.

The extraction conduit 62 may extend around the peripheral section 52 ofthe substrate table WT and may, in turn, be connected by one or moreconduits to an under pressure source which extracts the immersionliquid, for example in order to return the immersion liquid to areservoir.

As depicted in FIG. 6, the central section 51 of the substrate table WTincludes a thermal conditioning system which is arranged to thermallycondition the support section 53 of the substrate table WT. In otherwords, the thermal conditioning system is arranged to reduce or minimizeany variations in temperature of the support section 53, across thewidth of the support section 53 and/or over time.

The thermal conditioning system may comprise one or more apertures 72arranged to each or together provide a jet 71 of fluid, such as aliquid, onto the underside of the support section 53 of the substratetable WT. In this case, it will be understood that the underside of thesupport section 53 is the side of the support section 53 that isopposite to the side of the support section 53 that supports thesubstrate W. The provision of the jet 71 of liquid may efficientlyextract heat from the support section 53 of the substrate table WT.Accordingly, temperature variations of the support section 53 of thesubstrate table WT may be reduced.

The support section 53 may be selected to be as thermally conductive aspossible, subject to other constraints. Accordingly, the support section53 may be formed from a thermally conductive material, for exampleSiSiC. The support section 53 may also be as thin as possible, whilestill providing sufficient structural rigidity in order to support thesubstrate W.

The one or more apertures 72 may be formed in an aperture plate 73 thatis provided adjacent to the support section 53 such that the one or morejets 71 of liquid may be directed onto the underside of the supportsection 53. The or each aperture 72 is connected to a manifold 74arranged to distribute the liquid to the respective aperture 72.

As shown in FIG. 6, in an embodiment, the manifold 74 may be providedimmediately adjacent to the aperture plate 73. In particular, themanifold 74 may be partly formed by the aperture plate 73. Providing themanifold 74 as close as possible to the one or more apertures 72 mayreduce or minimize temperature variations in the liquid provided to theor each aperture 72. In turn, this may reduce temperature variations inthe support section 53.

As depicted in FIG. 6, an inlet 75 may be arranged to provide the liquidto the manifold 74 from a reservoir 76. In an embodiment, multipleopenings may be provided into the manifold 74 from the reservoir 76.This may further reduce the variation of temperature of liquid withinthe manifold 74. In turn this may further reduce the variation oftemperature of the jet 71 of liquid from the or each aperture 72.

The aperture plate 73 may be selected to reduce or minimize thermalconduction. This may reduce or minimize any temperature variations ofthe jet 71 of liquid provided by the or each aperture 72. Furthermore,if the aperture plate 73 forms part of the manifold 74, reducing thethermal conductivity of the aperture plate 73 may reduce any temperaturevariations of the liquid within the manifold 74. If the aperture plate73 forms part of the manifold 74 as depicted in FIG. 6, the apertureplate 73 may also be selected to provide sufficient stiffness to containthe liquid within the manifold 74 at the pressure necessary to providethe jet 71 of liquid. For example, the pressure may be, for example, 0.3to 1.5 bar.

The one or more apertures 72 may be provided in any suitablearrangement. For example, for a liquid pressure of 0.3 to 1.5 bar, theone or more apertures 72 may be, for example, 100 to 300 μm incross-sectional width (e.g., diameter). Furthermore, the aperture plate73 may include any number of apertures 72. For example, the apertureplate 73 may include, for example 500 to 5000 apertures 72, eachproviding a jet 71 of liquid to the underside of the support section 53.For an arrangement in which the one or more apertures 72 have the widthof approximately 100 μm, the depth of the manifold 74 may beapproximately 2 to 3 mm in order to provide an even distribution of theliquid to the one or more apertures 72.

As depicted in FIG. 6, in an embodiment, one or more thin walls 78 maybe provided to support the support section 53 above the aperture plate73. The one or more walls 78 may be configured to minimize or reduce thetransfer of heat between the support section 53 and the aperture plate73.

For example, as depicted in FIG. 6, the one or more walls 78 may beprovided in the form of hollow pillars. In such an arrangement, one ormore of the apertures 72 may be located within such a hollow pillar.Therefore a jet 71 of liquid may be provided within the hollow pillar.

In an embodiment, the hollow pillars may be circular or elliptical incross-section.

In an embodiment, the hollow pillars may be rectangular, for examplesquare, in cross-section. In such arrangement, some of the edges of thehollow pillars may be arranged to be parallel to the scanning directionof the substrate table WT in use. Alternatively or additionally, some ofthe edges may be aligned with another direction of movement of thesubstrate table, in which the substrate table may be moved at relativelyhigh acceleration. Such an arrangement may provide maximum rigidity inthe direction in which the substrate table WT undergoes the largestacceleration during use.

In an embodiment, the one or more walls 78 supporting the supportsection 53 from the aperture plate 73 may be provided in the form ofmultiple connecting ribs, namely planar sections of wall 78. Forexample, a plurality of planar sections of wall that are parallel toeach other may be provided. As with the rectangular cross-sectionpillars, the ribs may be oriented to be parallel to, for example, thescanning direction of the substrate table WT in use in order to maximizethe rigidity. It will be appreciated that in such arrangements, a linewithin a plane of the walls will be parallel to the scanning direction.

The one or more walls 78, regardless of their configuration, may bethermally conditioned by one or more appropriately oriented jets 71 ofliquid. Alternatively or additionally, the one or more walls 78 may beadequately thermally conditioned by liquid after it has been directedonto the underside of the support section 53.

Although not depicted in FIG. 6, it will be appreciated that one or moreopenings may be provided within the one or more walls 78 separating thesupport section 53 from the aperture plate 73 in order to permit themovement of the liquid after it has been directed onto the underside ofthe support section 53.

Furthermore, although not depicted in FIG. 6, one or more walls may beprovided within the manifold 74, for example supporting the apertureplate 73 in order to provide strength and rigidity to the manifold 74.The one or more walls within the manifold 74 may, for example, bearranged according to one of the arrangements discussed above for theone or more walls 78 supporting the support section 53.

In an embodiment, the central section 51 of the substrate table WT maybe separated from the peripheral section 52. For example, the centralsection 51 and the peripheral section 52 may be separated by anisolation system that is configured to reduce or minimize the transferof heat, or of vibrations, or of both between the central section 51 andthe peripheral section 52.

For example, as depicted in FIG. 6, in an embodiment, a gap 81 may beprovided between the central section 51 and the peripheral section 52.Accordingly, the central section 51 and the peripheral section 52 may beseparated by a distance of, for example, 50 to 300 μm. Although thecentral section 51 may be separated from the peripheral section 52, itwill be appreciated that sealing members 82,83 may be provided toprovide a liquid and/or gas type seal between portions of the centralsection 51 and the peripheral section 52, while reducing or minimizingthe possible transfer of heat and/or vibrations between the centralsection 51 and the peripheral section 52. For example, as shown in FIG.6, a sealing member (which may be referred to as a “sticker”), and whichmay be made from a metal, such as stainless steel, may be attachedbetween the lower surfaces of the central section 51 and the peripheralsection 52. Such a sealing member may contain the liquid after it hasbeen directed onto the underside of the support section 53 prior toextraction and return to the liquid reservoir 76, for example. It willbe appreciated that other known sealing members may be used.

In an embodiment, as depicted in FIG. 6, a sealing member 83 is providedbetween the central section 51 and the peripheral section 52 of thesubstrate table WT in order to seal a space 85 that is defined by thesupport section 53 of the substrate table WT, the aperture plate 73 anda portion of the peripheral section 52. As will be appreciated, the oneor more jets 71 of liquid are provided within this sealed space 85. Suchan arrangement may be beneficial because it may become fully humid inuse, namely saturated with the vapor of the liquid used in the thermalconditioning system. Evaporation of the liquid may be prevented,producing the possible causes of temperature variations within the space85.

In an embodiment, the space 85 is not sealed, for example by omittingthe second sealing member 83. Such an arrangement may beneficiallyenable non-uniform or fluctuating extraction rates of the liquid fromthe space 85.

In an embodiment, the system to extract liquid from the space 85 afterit has been directed onto the underside of the support section 53 of thesubstrate table WT may be specifically configured to help ensure thatthe aperture plate 73 always retains a continuous film of liquid acrossits entire surface shown, for example, as the line of short dashes inFIG. 6. This may reduce evaporation of the liquid from the surface ofthe aperture plate 73, reducing a possible source of temperaturevariation over the surface of the aperture plate 73, the surface of anynozzle in which the one or more apertures 72 are provided and/or thesurface of the one or more walls 78. However, it may be desirable tominimize the thickness of any layer of liquid on the surface of theaperture plate 73. This may reduce the mass of the substrate table WT inuse. In addition, this may reduce the effects of sloshing of the liquidcaused by the movement of the substrate table WT in use.

As noted above, a variety of liquids or other fluids may be used withinthe thermal conditioning system. For example, the liquid may be water.In an embodiment, the liquid may be the same as the immersion liquid. Insuch an arrangement, a single extraction system may be used to extractliquid from the drain that receives immersion liquid that leaks into thegap 55 between the edge of the substrate on the substrate table and theedge of the recess, and the liquid after it has been directed onto theunderside of the support section 53 of the substrate table WT. In anembodiment, the liquid used in the thermal conditioning system may be athermally conductive and electrically insulating liquid, such asFluorinert, manufactured by 3M.

In an embodiment, as depicted in FIG. 6, one or more openings 91 may beprovided from a part of the space 85 in which the one or more jets 71 ofliquid are provided to the extraction conduit 62 that is used to extractthe liquid from the drain. Accordingly, a common conduit 62 may be usedand may return liquid to a common reservoir 76. The liquid may besuitably conditioned before it is returned to the reservoir 76.

In an embodiment, downstream of the one or more openings 61 and the oneor more openings 91, the extraction conduit 62 may be provided with avent with a suitable flow restrictor. This may reduce the pressurefluctuation inside the space 85 in which the one or more jets 71 ofliquid are provided, even when there are fluctuations in the extractionpressure.

In an embodiment, a flow restrictor 92 may be provided to restrict theflow of liquid from the space 85 in which the one or more jets 71 ofliquid are provided into the extraction conduit 62. It will beappreciated that the positioning of the one or more openings 91 and theconfiguration of any flow restrictor 92 may be used in order to controlthe level of the liquid within the space 85.

In an embodiment, which is depicted in FIG. 19 and is a variation of theembodiment depicted in FIG. 6, a wall 170 may be provided within thespace 85 within which the one or more jets 71 of liquid are provided. Asshown in FIG. 19, the wall 170 may function as a dam, separating theregion surrounding the one or more apertures 72 from the one or moreopenings 91 into the conduit 62. The wall 170 may be used to help ensurethe level of the liquid within the space around the one or more jets 71of liquid. The wall 170 may assist in ensuring that only liquid isextracted through the one or more openings 91 into the conduit 62.

In an embodiment, the flow of liquid through the common extractionconduit 62 within the peripheral section 52 of the substrate table WTmay be used in order to thermally condition the peripheral section 52.For example, the common extraction conduit 62 may be arranged such thatthe liquid flows throughout the peripheral section 52 of the substratetable WT. In this respect, it may be noted that the temperature changeof the liquid that has been directed onto the underside of the supportsection 53 of the substrate table WT may be of the order of 18 to 24 mK.Accordingly, the liquid extracted from the space 85 in which the one ormore jets 71 of liquid are provided may be adequate for thermallyconditioning the peripheral section 52 of the substrate table WT.Alternatively or additionally, in an embodiment, a heater 95 may beprovided within the peripheral section 52 of the substrate table WT inorder to provide thermal conditioning of the peripheral section 52.

FIG. 7 depicts an arrangement of a substrate table WT that is similar tothe embodiment discussed above in relation to FIG. 6 but differs in thearrangement of the drain. For brevity, only the differences will bediscussed. In particular, in the arrangement depicted in FIG. 7, thedrain is configured such that a narrowed gap 101 is provided directlybelow the gap 55 between the edge of the substrate W and the edge of therecess within the substrate table WT. Extraction through the drain maybe used to prevent or reduce leakage of liquid to the underside of thesubstrate W.

As depicted in FIG. 7, the narrowed gap 101 may be provided between aprojection on the support section 53 of the central section 51 of thesubstrate table WT and a projection on the edge of the peripheralsection 52 of the substrate table WT. It should be appreciated, however,that although in FIG. 7 the projections are presented as being the samesize, this is not necessarily the case. Indeed, either projection may belarger than the other or may be omitted.

Immediately below the narrowed gap 101, a chamber 102 is provided whichis in fluid communication with the atmosphere above the substrate tableWT. In an embodiment, a line can be drawn straight down from the outsideof the substrate table WT through the narrowed gap 101 between theprojections into the chamber 102. In an embodiment, that line is avertical line and/or intercepts the boundary of the chamber 102 on abottom wall of the chamber 102. If the dimensions of the narrowed gap101 and the chamber 102 are correctly chosen, this arrangement may havean advantage that a gas knife, which may be used in the liquid supplysystem in order to help contain liquid, is not influenced by thepresence of the gap 101 because the gas knife does not “feel” the bottomof the chamber 102.

In an embodiment, the pressure of gas in the chamber 102 is maintainedat the same pressure as gas outside of the substrate table WT (i.e.ambient gas pressure). This means that there is, in normal operation,substantially no gas flow through the gap 101 when the gap 101 is notcovered by the liquid supply system and one or more gas flow devices ofthe liquid supply system are blowing gas through the gap 55. Even if theliquid supply system covers part of the gap 55, ambient pressure maystill be maintained in the chamber 102 because the chamber 102 isannular (or another shape that extends around the peripheral section 52of the substrate table WT) and will be open to the atmosphere above thesubstrate table WT through the gap 55 at another location around theperiphery of the substrate W.

In order to remove liquid from the chamber 102, liquid may be removed ina manner that does not create an under pressure in the chamber 102. Forexample, liquid may be removed from the chamber 102 using, for example,capillary action in a capillary passage 105 into an extraction conduit106. Alternatively, for example, one or more liquid removal devices maybe provided, for example which only apply an under pressure to passage105 when the presence of liquid at the mouth of the passage 105 in thechamber 102 is detected. Alternatively or additionally, a microsievesingle phase extractor (see European patent application publication no.EP 1 628 163, for example) may be used to remove liquid from the chamber102.

Alternatively or additionally, a controller may control whether an underpressure source is connected to a portion of the chamber 102 when theliquid supply system 12, which supplies liquid to only a localized areaof the substrate (in plan) at any one time, is located over the gap 55such that liquid in the liquid supply system drains into the gap 55.When the liquid supply system is not located over the gap 55, the underpressure source is not connected to the chamber 102. Thus, during mostof the time, the chamber 102 is at ambient pressure, but when liquid isdropping into the chamber 102 or is present in the chamber 102 an underpressure source is applied through a channel 105 to remove the liquidentering the chamber 102.

As with the arrangement in FIG. 6, in an arrangement having a drain asdiscussed above and as depicted in FIG. 7, a common extraction channelmay be used to extract the liquid that leaks through the gap 55 betweenthe edge of the substrate W and the edge of the recess, and the liquidthat has been directed onto the underside of the support section 53 ofthe substrate table WT. Accordingly, for example, the liquid that hasbeen directed onto the underside of the support section 53 may pass intothe chamber 102 that forms part of the drain within the peripheralsection of the substrate table WT.

If it is desired to seal the space 85 within which the one or more jets71 of liquid are provided, in an embodiment, a wall 110 may be providedto separate the space 85 from the chamber 102. As shown in FIG. 7, oneor more openings 111 may be provided to pass liquid from the space 85 inwhich the one or more jets 71 of liquid are provided into the chamber102.

FIG. 8 depicts a portion of a substrate table WT according to a furtherembodiment of the invention. Again, only the differences between thearrangement depicted in FIG. 6 and that depicted in FIG. 8 will bediscussed.

As shown in this embodiment, separate extraction conduits are providedfor the liquid to be extracted from the drain and for liquid to beextracted from the thermal conditioning system. Specifically, as shown,liquid that leaks through the gap 55 between the edge of the substrate Wand the edge of the recess in the substrate table WT may be extractedvia a first extraction conduit 62 within the peripheral section 52 ofthe substrate table WT. A second extraction conduit 120 may be providedto extract liquid from the space 85 within which the one or more jets 71of liquid are provided.

As shown, in an embodiment, the second extraction conduit 120 may beprovided within the peripheral section 52 of the substrate table WT.

It will be appreciated that the flow of liquid through the secondextraction conduit 120 may, in particular, be used to thermallycondition the peripheral section 52 of the substrate table WT. As withthe arrangement depicted in FIG. 6, a flow restrictor 91 may be providedin order to control the flow of liquid into the second extractionconduit 120.

The first and second extraction conduits 62, 120 may, as schematicallyrepresented in FIG. 8, return the liquid to a common reservoir 76.Alternatively, the first and second extraction conduits 62, 120 mayreturn liquid to separate reservoirs. Accordingly, the liquid extractedby the drain and the liquid used in the thermal conditioning system maybe kept separate. In either case, the liquid may be suitably conditionedbefore it is returned to the reservoir.

FIG. 9 schematically depicts a further embodiment of a substrate tableWT. As shown, in this embodiment, a drain arrangement such as thatdepicted in FIG. 7 and described above is provided but with a firstextraction conduit 106 for the drain and a second extraction conduit 125within the central portion 51 of the substrate table WT to extractliquid from the space 85 within which the one or more jets 72 of liquidas provided. In an embodiment, as depicted in FIG. 9, if it is desiredto seal the space 85 within which the one or more jets 71 of liquid areprovided, no openings may be provided in wall 126 that is provided toseparate the space 85 from the chamber 102 of the drain.

It should be appreciated that in embodiments such as that depicted inFIG. 9, in which separate extraction conduits 106,125 are provided forthe extraction of liquid from the drain and extraction of liquid fromthe thermal conditioning system, the separate extraction conduits mayreturn the liquid to a common reservoir 76 or to separate reservoirs.

FIGS. 10 to 13 depict further variations of the embodiments depicted inFIGS. 6 to 9, respectively. In each case, the only difference betweenthe embodiments is that the substrate table WT is not separated into acentral section and a peripheral section by an isolation system but is asingle integral substrate table. Accordingly, sealing members 82, 83shown in FIG. 6 are not required, for example.

In each of the embodiments discussed above in relation to FIGS. 6 to 13,the one or more jets 71 of liquid are provided from the or each aperture72 formed in one or more nozzles on the aperture plate 73. However, itshould be appreciated that one or more nozzles need not be provided.Accordingly, in embodiments of the invention which may be used inconjunction with any of the embodiments depicted in FIGS. 6 to 13, theone or more apertures 72 may be coplanar with the upper surface of theaperture plate 73. In other words, the one or more apertures 72 may beformed in the surface of the aperture plate 73 that faces the supportsection 53 of the recess in the substrate table WT. Such an arrangementis depicted in FIG. 14.

In an embodiment that may be combined with any of the embodimentsdiscussed above, the lower surface of the support section 53, namely thesurface on which the one or more jets 71 of liquid are directed, mayinclude an indent that is associated with the or each jet 71 of liquid.Such an arrangement is depicted in FIG. 15. The one or more indents 130may be arranged such that the liquid in the jet 71 of liquid that isdirected into the indent 130 is directed back towards the aperture plate73. For example, the liquid may be re-directed such that it does notinterfere with liquid from an adjacent jet. It should be appreciatedthat re-directed liquid from adjacent jets may combine when travelingback towards the aperture plate 73.

In an embodiment that may be combined with any of the embodimentsdiscussed above, the space 85 within which the one or more jets 71 ofliquid are provided may be entirely filled with the liquid such that theone or more jets 71 of liquid are provided within the bulk of liquid.

As discussed above, in any of the embodiments depicted in FIGS. 6 to 13,including embodiments combined with the arrangements depicted in FIGS.14 and/or 15, the extraction of liquid from the space 85 within whichthe one or more jets 71 of liquid are provided may be arranged such thatthere remains a permanent layer of liquid on the aperture plate 73. Aspreviously explained, it may be beneficial to ensure that this layer isas thin as possible in order to prevent sloshing. Alternatively oradditionally, as depicted in FIG. 16, a layer of porous material may beprovided on the aperture plate 73. The porous material may help ensurethat a continuous layer of liquid remains on the aperture plate 73,reducing the possible heat load caused by drying of portions of theaperture plate 73. The porous material 135 may prevent or reduce thesloshing of liquid during movement of the substrate table WT. The porousmaterial may be selected to have a relatively low thermal conductivity.For example, it may be formed from polytetrafluoroethylene (PTFE),ceramic such as Zerodur manufactured by Schott AG, quartz or polyacetalco-polymer (POM).

In any of the embodiments discussed above, the thermal conditioningsystem provides liquid to the support section 53 of the substrate tableWT in order to thermally condition the support section 53 and, in turn,the substrate W supported upon the support section 53. It will beappreciated that, in order to do so, the temperature of the liquid maybe carefully controlled.

In an embodiment, as depicted in FIGS. 6 and 17, a heater 141 and/or acooler 142 may be provided within the liquid reservoir 76 in order toadjust the temperature of the liquid within the reservoir 76. Inaddition a temperature sensor 143 may be provided in order to monitorthe temperature of the liquid within the reservoir 76. Data from thesensor 143 may be used to control the heater 141 and/or cooler 142.

Alternatively or additionally, a heater 145 and/or cooler 146 may beprovided within the manifold 74 in order to adjust the temperature ofthe liquid within the manifold 74. Likewise, a temperature sensor 147may be provided within the manifold 74. A temperature sensor 147 withinthe manifold 74 may be used to provide control of the heater 141 and/orcooler 142 in the liquid reservoir 76 and the heater 145 and/or cooler146 within the manifold 74. In either case, as depicted in FIG. 17, acontroller 150 may be provided to control one or more of the heaters141, 145 and/or coolers 142, 146 based on measurement data from thetemperature sensors 143, 147.

In an embodiment, alternatively or additionally a heater 152 may beprovided for one or more of the apertures 72 in order to adjust thetemperature of liquid forming an individual jet 71 of liquid. Atemperature sensor 153 may be provided downstream of the heater 152 inorder to provide measurement data for the control of the heater 152. Asdepicted in FIG. 17, the heater 152 and temperature sensor 153 may becontrolled by the controller 150.

It should be appreciated that such an arrangement may provide improvedcontrol of a thermal conditioning system. Accordingly, for example, itmay be possible to control the thermal conditioning system to provide aconsistent temperature across the support section 53 of the recesswithin the substrate table WT even when the heat load is not consistentacross the support section 53. Furthermore, for example, the thermalconditioning system may be able to compensate for both positive andnegative heat loads within the substrate table WT. Furthermore, forexample, the thermal conditioning system may provide faster thermalconditioning for a substrate table WT than previously known systems inwhich a liquid is passed through a channel within the substrate tableWT. This may be realized because each jet 71 may have its temperatureindividually controlled by a dedicated control loop comprising anactuator, such as a heater, and a feedback sensor, such as a temperaturesensor.

In an embodiment which may be combined with any of the embodimentsdiscussed above, additional thermal conditioning may be provided to theperipheral section 52 of the substrate table WT as show in FIG. 18. Inparticular, the thermal conditioning system may be configured to provideone or more apertures 160 configured to direct one or more jets 161 ofliquid in order to thermally condition a part 162 of the peripheralsection 52 of the substrate table WT. It should be appreciated that suchan arrangement may be provided within a substrate table WT that does notinclude a drain arrangement as discussed above. In other words, thethermal conditioning system may be configured to thermally conditionboth a central section of a substrate table WT which supports asubstrate W and a peripheral section of the substrate table WT thatsurrounds the substrate W and may, for example, have an upper surfacewhich is coplanar with an upper surface of the substrate W whensupported on the substrate table WT.

FIG. 18 schematically depicts an arrangement for an embodiment includinga drain corresponding to that depicted in FIG. 6. As shown, the thermalconditioning system is provided to thermally condition the top surfaceof the peripheral section 52 of the substrate table WT. The top surface162 may, for example, be configured to be coplanar with the uppersurface of a substrate W supported within the recess of the substratetable WT. As shown, the thermal conditioning system provides one or morejets 161 of liquid to the underside of the top surface 162 of theperipheral section 52 of the substrate table WT in a manner similar tothat discussed above in relation to the thermal conditioning of thesupport section 53 of the recess. It should be appreciated thatvariations of the arrangements for thermally conditioning the supportsection 53 of the recess discussed above may apply to the thermalconditioning of the top surface 162 of the peripheral section 52 of thesubstrate table WT.

As depicted in FIG. 18, liquid maybe extracted from the thermalconditioning system within the peripheral section 52 of the substratetable WT after it has been directed onto the lower surface of the upperface 162 of the peripheral section 52. It should be appreciated that theliquid extraction may be performed by a separate extraction conduit tothose previously discussed above. Alternatively, the extraction may becombined with any of the extraction conduits previous discussed.

As will be appreciated, any of the above described features can be usedwith any other feature and it is not only those combinations explicitlydescribed which are covered in this application.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications in manufacturing components with microscale, or evennanoscale, features, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 248, 193, 157 or 126 nm). The term“lens”, where the context allows, may refer to any one or combination ofvarious types of optical components, including refractive and reflectiveoptical components.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. For example, the embodiments of the invention maytake the form of a computer program containing one or more sequences ofmachine-readable instructions describing a method as disclosed above, ora data storage medium (e.g. semiconductor memory, magnetic or opticaldisk) having such a computer program stored therein. Further, themachine readable instruction may be embodied in two or more computerprograms. The two or more computer programs may be stored on one or moredifferent memories and/or data storage media.

One or more controllers described herein may each or in combination beoperable when the one or more computer programs are read by one or morecomputer processors located within at least one component of thelithographic apparatus. The controllers may each or in combination haveany suitable configuration for receiving, processing, and sendingsignals. One or more processors are configured to communicate with theat least one of the controllers. For example, each controller mayinclude one or more processors for executing the computer programs thatinclude machine-readable instructions for the methods described above.The controllers may include data storage medium for storing suchcomputer programs, and/or hardware to receive such medium. So thecontroller(s) may operate according the machine readable instructions ofone or more computer programs.

One or more embodiments of the invention may be applied to any immersionlithography apparatus, in particular, but not exclusively, those typesmentioned above and whether the immersion liquid is provided in the formof a bath, only on a localized surface area of the substrate, or isunconfined. In an unconfined arrangement, the immersion liquid may flowover the surface of the substrate and/or substrate table so thatsubstantially the entire uncovered surface of the substrate table and/orsubstrate is wetted. In such an unconfined immersion system, the liquidsupply system may not confine the immersion liquid or it may provide aproportion of immersion liquid confinement, but not substantiallycomplete confinement of the immersion liquid.

A liquid supply system as contemplated herein should be broadlyconstrued. In certain embodiments, it may be a mechanism or combinationof structures that provides a liquid to a space between the projectionsystem and the substrate and/or substrate table. It may comprise acombination of one or more structures, one or more fluid openingsincluding one or more liquid openings, one or more gas openings or oneor more openings for two phase flow. The openings may each be an inletinto the immersion space (or an outlet from a fluid handling structure)or an outlet out of the immersion space (or an inlet into the fluidhandling structure). In an embodiment, a surface of the space may be aportion of the substrate and/or substrate table, or a surface of thespace may completely cover a surface of the substrate and/or substratetable, or the space may envelop the substrate and/or substrate table.The liquid supply system may optionally further include one or moreelements to control the position, quantity, quality, shape, flow rate orany other features of the liquid.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

In an embodiment, there is provided an immersion lithographic apparatus,comprising: a substrate table, including a recess having a supportsection configured to support a substrate; a drain in the substratetable, configured to receive an immersion fluid which leaks, in use,into a gap between an edge of a substrate on the substrate table and anedge of the recess; and a thermal conditioning system, configured tothermally condition the support section of the recess; wherein thethermal conditioning system comprises at least one aperture, configuredto direct a jet of fluid onto a reverse side of the support section ofthe recess that is opposite to a support side that supports thesubstrate.

In an embodiment, the substrate table includes a central section and aperipheral section that surrounds the central section; the recess isformed in the central section; and the drain is formed in the peripheralsection.

In an embodiment, the central section and the peripheral section areseparated from each other by an isolation system that is configured tominimise the transfer of at least one of heat and vibrations between thecentral section and the peripheral section.

In an embodiment, the thermal conditioning system is configured tothermally condition the peripheral section of the substrate table.

In an embodiment, the peripheral section of the substrate table includesa planar section having an upper surface which, in use, is parallel toan upper surface of a substrate supported in the recess, and a lowersurface; and the thermal conditioning system comprises at least oneaperture, configured to direct a jet of fluid onto the lower surface ofthe planar section of the peripheral section of the substrate table.

In an embodiment, the immersion lithographic apparatus comprises a fluidextraction system; and the fluid extraction system is configured toextract fluid that has been directed onto the reverse side of thesupport section of the recess.

In an embodiment, the fluid extraction system is configured such thatfluid extracted after it has been directed onto the reverse side of thesupport section of the recess passes through at least one conduit in theperipheral section of the substrate table; and the at least one conduitforms part of the thermal conditioning system and is used to thermallycondition the peripheral section.

In an embodiment, the fluid extraction system is further configured toextract fluid from the drain.

In an embodiment, the fluid extraction system is configured such thatfluid extracted from the drain and fluid extracted after it has beendirected onto the reverse side of the support section of the recess isextracted through a common conduit in the peripheral section of thesubstrate table.

In an embodiment, the fluid extraction system is configured such thatfluid extracted from the drain is extracted through a first conduit inthe peripheral section of the substrate table and fluid extracted afterit has been directed onto the reverse side of the support section of therecess is extracted through a second conduit in the peripheral sectionof the substrate table.

In an embodiment, the immersion lithographic apparatus comprises a fluidextraction system; and the fluid extraction system is configured toextract fluid from the drain and to extract fluid from the thermalconditioning system after it has been directed onto the reverse side ofthe support section of the recess.

In an embodiment, the fluid extracted from the drain and fluid extractedafter it has been directed onto the reverse side of the support sectionof the recess is extracted through a common conduit in the substratetable.

In an embodiment, the fluid extraction system is configured such thatfluid extracted from the drain is extracted through a first conduit inthe substrate table and fluid extracted after it has been directed ontothe reverse side of the support section of the recess is extractedthrough a second conduit in the peripheral section of the substratetable.

In an embodiment, the fluid extraction system comprises a fluid flowrestrictor arranged to restrict the flow of fluid into the commonconduit after it has been directed onto the reverse side of the supportsection of the recess.

In an embodiment, the thermal conditioning system comprises an apertureplate, in which the at least one aperture is provided; wherein theaperture plate is provided adjacent the support section of the recesssuch that a respective jet of fluid provided by the at least oneaperture is directed onto the reverse side of the support section of therecess.

In an embodiment, each of the at least one apertures is formed in arespective nozzle which protrudes from the aperture plate in thedirection of the support section of the recess.

In an embodiment, the at least one aperture is coplanar with a surfaceof the aperture plate that faces the support section of the recess.

In an embodiment, the support section of the recess is supported by aplurality of thin walls in turn supported by the aperture plate.

In an embodiment, the plurality of thin walls include at least onehollow pillar; and at least one aperture in the aperture plate isprovided such that the corresponding jet of fluid is provided with thehollow pillar.

In an embodiment, the immersion lithographic further comprises anactuator system configured to move the substrate table, in use, in ascanning direction; and a plurality of the thin walls are planar andarranged such that a line within the plane of the walls is parallel tothe scanning direction.

In an embodiment, the aperture plate and the support section of therecess in part define a space which is sealed apart from the at leastone aperture and at least one outlet for extracting the fluid after ithas been directed onto the reverse side of the support section of therecess.

In an embodiment, the at least one outlet is arranged such that, in use,a continuous film of fluid covers the aperture plate.

In an embodiment, a porous material is provided on the aperture plate.

In an embodiment, the thermal conditioning system is configured suchthat, in use, the space is filled with fluid.

In an embodiment, the reverse side of the support section of the recessincludes an indent associated with each jet of fluid, which isconfigured such that the fluid directed into the indent is directed backtowards the aperture plate.

In an embodiment, the thermal conditioning system includes a fluidmanifold configured to provide fluid to the at least one aperture in theaperture plate.

In an embodiment, the manifold is provided in a space on the oppositeside of the aperture plate to the support section of the recess.

In an embodiment, the fluid is provided from a fluid reservoir to themanifold through one or a plurality of openings into the manifold.

In an embodiment, at least one of a cooler and a heater is provided inat least one of the fluid reservoir and the manifold.

In an embodiment, at least one of a heater and a cooler is providedupstream of each of the at least one aperture and arranged to heat orcool the fluid before it exits the respective aperture.

In an embodiment, the lithographic apparatus further comprises at leastone temperature sensor downstream of the at least one heater and cooler;and a controller configured to control the at least one heater andcooler based on measurement data from the at least one temperaturesensor.

In an embodiment, the peripheral section of the substrate tablecomprises a heater arranged to heat directly the peripheral section ofthe substrate table.

In an embodiment, there is provided a device manufacturing methodcomprising: providing a substrate to a recess in a substrate table, therecess having a support section configured to support the substrate;providing immersion fluid to an upper surface of the substrate;extracting immersion fluid that leaks into a gap between an edge of thesubstrate and an edge of the recess through a drain in the substratetable; and thermally conditioning the support section of the recess bydirecting at least one jet of fluid onto a reverse side of the supportsection of the recess that is opposite a support side that supports thesubstrate.

In an embodiment, there is provided a lithographic apparatus,comprising: a substrate table, including a recess having a supportsection configured to support a substrate and a peripheral section,surrounding the recess; and a thermal conditioning system, configured tothermally condition the support section of the recess and the peripheralsection of the substrate table; wherein the thermal conditioning systemcomprises at least one aperture, configured to direct a jet of fluidonto a reverse side of the support section of the recess that isopposite to a support side that supports the substrate, and at least oneaperture, configured to direct a jet of fluid onto a portion of theperipheral section of the substrate table.

In an embodiment, there is provided a device manufacturing methodcomprising: providing a substrate to a recess in a substrate table, therecess having a support section configured to support the substrate andthe substrate table having a peripheral section surrounding the recess;thermally conditioning the support section of the recess by directing atleast one jet of fluid onto reverse side of the support section of therecess that is opposite a support side that supports the substrate; andthermally conditioning the peripheral section of the substrate table bydirecting at least one jet of fluid onto a portion of the peripheralsection of the substrate table.

The invention claimed is:
 1. An A substrate table for an immersionlithographic apparatus, the immersion lithographic apparatus comprising:a projection system configured to project radiation onto a substrate,wherein the substrate table comprising comprises: a recess having acentral support section configured to support a the substrate, thecentral support section having: a support surface having a protrusion tocontact a bottom surface of the substrate, a lateral surface at anon-zero angle non-parallel to the support surface, and a bottom surfaceat a non-zero angle non-parallel to the lateral surface and facing awayfrom the support surface, the lateral surface extending to the bottomsurface of the central support section; and a peripheral section of thesubstrate table that surrounds the central support section and definesthe recess, the peripheral section being effectively thermally isolatedfrom the central support section, and the peripheral section comprising:a drain opening arranged to face the recess and configured to receive animmersion fluid which leaks, in use, into a gap between an edge of thesubstrate when supported on the substrate table and an edge of therecess, the drain opening located above the bottom surface of thecentral support section and a cross-section across the face of the drainopening is arranged to be non-parallel to the support surface, and alateral surface facing, and spaced by an open qap gap from, the lateralsurface of the central support section, wherein the lateral surface ofthe peripheral section is outward, in a horizontal direction, of anouter periphery of the bottom surface of the substrate when supported onthe substrate table; and a projection system configured to projectradiation onto the substrate a heater and/or a channel configured toconvey a heat transfer fluid.
 2. The immersion lithographic apparatussubstrate table of claim 1, further comprising a solid member spanningthe open gap to directly connect the central support section and theperipheral section.
 3. The immersion lithographic apparatus substratetable of claim 2, wherein the open gap extends below the member.
 4. Theimmersion lithographic apparatus substrate table of claim 2, wherein themember is a separate body from the central support section and theperipheral section.
 5. The immersion lithographic apparatus substratetable of claim 2, wherein the member is configured to reduce transfer ofvibrations between the peripheral section and the central supportsection.
 6. The immersion lithographic apparatus substrate table ofclaim 1, wherein a continuous open gap, including the gap and the opengap, separates the central support section and the peripheral sectionssection from the top of the central support section and peripheralsection to the bottom of the central support section and peripheralsection.
 7. The immersion lithographic apparatus substrate table ofclaim 1, wherein the drain opening is located in a side surface of theperipheral section, the side surface at a non-zero angle non-parallel tothe support surface.
 8. The immersion lithographic apparatus substratetable of claim 1, wherein the peripheral section comprises a heaterarranged to heat directly the peripheral section.
 9. An A substratetable for an immersion lithographic apparatus, the immersionlithographic apparatus comprising: a projection system configured toproject radiation onto a substrate, wherein the substrate tablecomprising comprises: a recess having a central support sectionconfigured to support a the substrate, the central support sectionhaving a support surface having a protrusion to contact a bottom surfaceof the substrate and having a lateral surface at a non-zero anglenon-parallel to the support surface, and a peripheral section of thesubstrate table that surrounds the central support section and definesthe recess, the peripheral section being effectively thermally isolatedfrom the central support section and the substrate when supported on thecentral support section, and the peripheral section comprising a drainopening arranged to face the recess and configured to receive animmersion fluid which leaks, in use, into a gap between an edge of thesubstrate when supported on the substrate table and an edge of therecess, wherein a cross-section across the face of the drain opening isarranged to be non-parallel to the support surface and wherein at leastpart of the lateral surface of the central support section is spaced byan open gap from at least part of a lateral surface of the peripheralsection, the lateral surface of the peripheral section is outward, in ahorizontal direction, of an outer periphery of the bottom surface of thesubstrate when supported on the substrate table, and a solid memberspanning the open gap to directly connect the central support sectionand the peripheral section; and a projection system configured toproject radiation onto the substrate.
 10. The immersion lithographicapparatus substrate table of claim 9, wherein the open gap extends belowthe member.
 11. The immersion lithographic apparatus substrate table ofclaim 9, wherein the member is a separate body from the central supportsection and the peripheral section.
 12. The immersion lithographicapparatus substrate table of claim 9, wherein the member is configuredto reduce transfer of vibrations between the peripheral section and thecentral support section.
 13. The immersion lithographic apparatussubstrate table of claim 9, wherein the drain opening is located in aside surface of the peripheral section, the side surface at a non-zeroangle non-parallel to the support surface.
 14. The immersionlithographic apparatus substrate table of claim 9, wherein theperipheral section comprises a heater arranged to heat directly theperipheral section.
 15. A device manufacturing method comprising:providing a substrate to a recess in a substrate table, the recesshaving a central support section supporting the substrate, the centralsupport section having: a support surface having a protrusion thatcontacts a bottom surface of the substrate, a lateral surface at anon-zero angle non-parallel to the support surface, and a bottom surfaceat a non-zero angle non-parallel to the lateral surface and facing awayfrom the support surface, the lateral surface extending to the bottomsurface of the central support section; providing immersion fluid to anupper surface of the substrate and/or the substrate table; draining theimmersion fluid that leaks into a gap between an edge of the substratesupported on the substrate table and an edge of the recess through adrain opening located in a peripheral section of the substrate table,the drain opening facing the recess and located above the bottom surfaceof the central support section and a cross-section across the face ofthe drain opening is non-parallel to the support surface, the peripheralsection surrounding the central support section and defining the recess,and the peripheral section being effectively thermally isolated from thecentral support section and the substrate supported on the centralsupport section, wherein a lateral surface of the peripheral sectionfaces, and is spaced by an open gap from, the lateral surface of thecentral support section, the lateral surface of the peripheral sectionbeing outward, in a horizontal direction, of an outer periphery of thebottom surface of the substrate; and providing thermal transfer in thesubstrate table using a heater and/or a channel configured to convey aheat transfer fluid; and projecting radiation onto the substrate. 16.The method of claim 15, wherein the peripheral section is effectivelymechanically isolated from the central support section.
 17. The methodof claim 15, wherein a solid member spans the open gap to directlyconnect the central support section and the peripheral section.
 18. Themethod of claim 17, wherein the open gap extends below the member. 19.The method of claim 17, wherein the member is configured to reducetransfer of vibrations between the peripheral section and the centralsupport section.
 20. The immersion lithographic apparatus substratetable of claim 1, wherein the peripheral section is effectivelymechanically isolated from the central support section.
 21. Theimmersion lithographic apparatus substrate table of claim 9, wherein theopen gap extends around the central support section, wherein anuppermost surface of the peripheral section adjacent the substrate whensupported on the substrate table is generally coplanar with an uppersurface of the substrate when supported on the substrate table, andwherein the drain opening is located above the member.
 22. Alithographic apparatus comprising: the substrate table of claim 1; and aprojection system configured to project a pattern from a patterningdevice onto a substrate using a projection beam; and a liquid supplysystem configured to supply a liquid to a space between the projectionsystem and the substrate table.
 23. A lithographic apparatus comprising:the substrate table of claim 9; and a projection system configured toproject a pattern from a patterning device onto a substrate using aprojection beam; and a liquid supply system configured to supply aliquid to a space between the projection system and the substrate table.